Influence of the Collision Energy on the O(1D) + RH → OH(X2Π) + R (RH = CH4, C2H6, C3H8) Reaction Dynamics:  A Laser-Induced Fluorescence and Quasiclassical Trajectory Study

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Articles you may be interested inThe lowest doublet and quartet potential energy surfaces involved in the N ( 4 S)+ O 2 reaction. II. Ab initio study of the C 2v -symmetry insertion mechanism Ab initio, VTST, and QCT study of the 1 2 A ″ potential energy surface of the N ( 2 D)+ O 2 (X 3 Σ g − )→ O ( 3 P)+ NO (X 2 Π) reaction This work presents two new analytical fits of the ground potential energy surface ͑PES͒ ( 3 AЉ) and the first excited PES ( 3 AЈ) involved in the title reaction, considering the N-abstraction ͑1͒ and the O-abstraction ͑2͒ reaction channels, and the reverse reaction ͑Ϫ1͒. The PESs are derived from ab initio electronic structure calculations by means of second-order perturbation theory on a complete active-space self-consistent-field wave function ͑CASPT2 method͒. Stationary points and extensive grids of ab initio points ͑about 5600 points for the 3 AЉ PES and 4900 points for the 3 AЈ PES͒ were fitted along with some diatomic spectroscopic data to better account for the experimental exoergicity. Thermal rate constants were calculated ͑200-5000 K͒ for all mentioned reaction processes by means of the variational transition-state theory with the inclusion of a semiclassical tunneling correction. Excellent agreement with the experimental data was observed for reaction ͑1͒ and its reverse, within all the temperature range, substantially improving the results derived from previous analytical PESs. The contribution of the 3 AЈ PES to the reaction rate constant (k 1 ) was small even at high temperatures ͑e.g., only 10.8% at 2500 K͒. Moreover, the main contribution to reaction rate constant (k 2 ) was due to the 3 AЈ PES, differing from what happens for reaction ͑1͒.The O-abstraction reaction channel accounts for a 3.0% of the total reaction (kϭk 1 ϩk 2 ) at 5000 K, consistent with the very limited experimental information available.

Section: Variational Transition-state Thermal Rate Constantsmentioning

confidence: 99%

Ab initio derived analytical fits of the two lowest triplet potential energy surfaces and theoretical rate constants for the N(4S)+NO(X 2Π) system

Gamallo

González

Sayós

2003

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“…[4][5][6] The CH 3 OH reaction intermediate can be formed rather easily via insertion of O( 1 D) into a C-H bond of methane. 4,6,24,36,37 The particular importance of the CH 3 + OH channel (which has a kinematics nearly identical to reactants) is probably due to the fact that the other channels are less exoergic or present a barrier with respect to CH 3 OH.…”

Section: Introductionmentioning

confidence: 99%

“…14,15 The effect of the O( 1 D) + CH 4 collision energy (relative translational energy of reactants, E c ) on the OH product vibrational state distributions, has been measured by infrared (IR) emission and related techniques 20, 25 and by laser-induced fluorescence (LIF). 19,[21][22][23][24] The rotational state distributions were also determined experimentally in Refs. 19 and 22-24.…”

Section: Introductionmentioning

confidence: 99%

Quantum dynamical study of the O(1D) + CH4 → CH3 + OH atmospheric reaction

Bouchrit

Jorfi

Abdallah

et al. 2014

Time independent quantum mechanical (TIQM) scattering calculations have been carried out for the O((1)D) + CH4(X(1)A1) → CH3(X(2)A2″) + OH(X(2)Π) atmospheric reaction, using an ab initio ground potential energy surface where the CH3 group is described as a pseudo-atom. Total and state-to-state reaction probabilities for a total angular momentum J = 0 have been determined for collision energies up to 0.5 eV. The vibrational and rotational state OH product distributions show no specific behavior. The rate coefficient has been calculated by means of the J-shifting approach in the 10-500 K temperature range and slightly depends on T at ordinary temperatures (as expected for a barrierless reaction). Quantum effects do not influence the vibrational populations and rate coefficient in an important way, and a rather good agreement has been found between the TIQM results and the quasiclassical trajectory and experimental ones. This reinforces somewhat the reliability of the pseudo-triatomic approach under the reaction conditions explored.

“…Similar bimodal distributions to some extent have rather been observed in the exothermic reactions of electronically excited atomic oxygen O( 1 D) with saturated hydrocarbon reactions. [13][14][15][16][17][18] Wiesenfeld et al found that the major high-NЉ regime ͑about 80% of the relative yields͒ was ascribed to the short-lived insertion process and adequately described by the linear surprisal. It was also possible to deduce the population of the low-NЉ regime by subtracting the prior distribution scaled by the surprisal parameter from the nascent distribution.…”

Section: Reaction Mechanismmentioning

confidence: 99%

“…In addition, two microscopic reaction pathways for the minor OH channel have been proposed to understand the characteristic bimodal rotational distributions of OH product: the low-and high-NЉ components. [13][14][15][16][17][18][19][20][21][22] While the low-NЉ components are formed from the long-lived alcohol intermediate produced by the insertion reaction of O( 1 D) into a C-H bond, the high-NЉ components are characterized by the process undergoing a short-lived insertion complex.…”

Section: Introductionmentioning

confidence: 99%

Atom-radical reaction dynamics of O(3P)+C3H5→C3H4+OH: Nascent rovibrational state distributions of product OH

Park

Lee

Kwon

et al. 2002

The reaction dynamics of ground-state atomic oxygen ͓O( 3 P)͔ with allyl radicals (C 3 H 5 ) has been investigated by applying a combination of crossed beams and laser induced fluorescence techniques. The reactants O( 3 P) and C 3 H 5 were produced by the photodissociation of NO 2 and the supersonic flash pyrolysis of precursor allyl iodide, respectively. A new exothermic channel of O( 3 P) ϩC 3 H 5 →C 3 H 4 ϩOH was observed and the nascent internal state distributions of the product OH (X 2 ⌸:Љϭ0,1) showed substantial bimodal internal excitations of the low-and high-NЉ components without ⌳-doublet and spin-orbit propensities in the ground and first excited vibrational states. With the aid of the CBS-QB3 level of ab initio theory and Rice-Ramsperger-Kassel-Marcus calculations, it is predicted that on the lowest doublet potential energy surface the major reaction channel of O( 3 P) with C 3 H 5 is the formation of acrolein (CH 2 CHCHO)ϩH, which is consistent with the previous bulk kinetic experiments performed by Gutman et al. ͓J. Phys. Chem. 94, 3652 ͑1990͔͒. The counterpart C 3 H 4 of the probed OH product in the title reaction is calculated to be allene after taking into account the factors of reaction enthalpy, barrier height and the number of intermediates involved along the reaction pathway. On the basis of population analyses and comparison with prior calculations, the statistical picture is not suitable to describe the reactive atom-radical scattering processes, and the dynamics of the title reaction is believed to proceed through two competing dynamical pathways. The major low NЉ-components with significant vibrational excitation may be described by the direct abstraction process, while the minor but extraordinarily hot rotational distribution of high NЉ-components implies that some fraction of reactants is sampled to proceed through the indirect short-lived addition-complex forming process.